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Scientist Plays Down Danger of Flu Strain

A Wisconsin virology team that created a more contagious form of bird flu did not produce a highly lethal superflu, as a Dutch team famously and controversially did last year, according to the leader of the Wisconsin team.

Dr. Yoshihiro Kawaoka of the University of Wisconsin-Madison and the University of Tokyo said in a commentary published online by Nature magazine that his team’s virus had infected ferrets through the air, but that it did not kill any of them. Ferrets catch flu just as humans do. Also, he said, “Current vaccines and antiviral compounds are effective against it.”

By contrast, a virus created by Ron Fouchier of Erasmus Medical Center in the Netherlands had both the high lethality of the H5N1 avian flu and the ability to transmit easily among ferrets, touching off fears that his virus could be devastating in people.

However, a flu expert who serves on an American scientific advisory panel that looked at both Dr. Fouchier’s work and Dr. Kawaoka’s said the panel still believed key details should be censored from both papers before they are published to keep terrorists or rogue scientists from being to replicate the work, since the gene-manipulation techniques and intermediate mutations are as potentially dangerous as the end products.

Some scientists believe that Dr. Fouchier created what is potentially the most lethal virus in history — a flu that would transmit through a sneeze and kill more than 50 percent of those who caught it. That has led to calls for restrictions. Some — including the editorial board of The New York Times — have argued that the virus stocks should be destroyed; others want the virus restricted to a small number of laboratories with the highest biosecurity levels.

Some scientists, including Dr. Fouchier, argue that the fear of his virus is exaggerated. What works in ferrets does not always work in humans, they argue, and the true lethality of avian H5N1 is unknown because there have been fewer than 600 confirmed human cases and many milder ones might exist.

The debate about Dr. Kawaoka’s work is likely to be less heated since what he produced is less dangerous.

In his commentary for Nature, published online on Wednesday, Dr. Kawaoka said his team took the hemagglutinin gene from the avian H5N1 — which produces the “spike” that allows it to attach to receptors on cells in the human nose — and attached it to the other seven genes of the virus that caused the H1N1 “swine flu” pandemic in 2009.

That virus — once called “a real mutt” by a top virologist — was a novel mixture of genes from flus previously found in humans, birds, North American pigs and Eurasian pigs. It spread easily through humans but — despite having caused panic when it filled emergency rooms in Mexico City, where it was first noticed — ultimately turned out to be less lethal than most seasonal flus.

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In an e-mail message, Dr. Kawaoka said that there were some mutations in the hemagglutinin gene he got from avian H5N1, but that he “could not comment on the specifics.”

A vaccine created to protect humans against infection with avian H5N1 virus also worked against his version of the virus, he said.

Asked if it was possible that his virus could be passed around among laboratories for further work while Dr. Fouchier’s virus ought to be more highly restricted, he said, “That judgment has to be made in discussions with the international scientific community.”

After reading Dr. Kawaoka’s commentary, Dr. Fouchier said it appeared that Dr. Kawaoka’s virus was less lethal than the one he created, although he reiterated that he did not think what he had created was as dangerous as it had been portrayed.

But, he said, “I have not seen Kawaoka’s data, so I would not know the details of his study.”

Richard H. Ebright, a chemistry professor and bioweapons expert at Rutgers University who has long opposed unrestricted research into making flu viruses more lethal, said his impression was that Dr. Kawaoka’s virus was less lethal than Dr. Fouchier’s, but that if the only vaccine against it was an experimental H5N1 vaccine that is not widely stockpiled, “it still has significant pandemic potential.”

Even if the virus is safe enough to be studied in labs with only medium-high biosecurity levels, he said, “This virus will not be the endpoint; the first experiment that will be done with it will be an effort to enhance its lethality.” That process, he argued, should not go forward without national or international review.

“These are decisions that cannot be left to the individual investigators,” he said.

Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota and a member of the National Science Advisory Board for Biosecurity, said the panel still wanted the details of Dr. Kawaoka’s work censored as it did Dr. Fouchier’s.

“We have concerns both about the organisms and about how you manufacture them,” he said.

A version of this article appears in print on January 26, 2012, on Page A16 of the New York edition with the headline: Scientist Plays Down Danger of Flu Strain. Order Reprints|Today's Paper|Subscribe